The present invention relates to a brake control system for use in motor vehicle which is arranged so as to perform the brake control by increasing and decreasing the braking hydraulic pressure in the wheel-braking cylinder, and further to a restriction adjusting valve suitable for the brake control.
Conventional vehicle brake control systems such as an anti-skid control apparatus are generally arranged to adjust the braking hydraulic pressure with a switching operation between pressure-increasing, pressure-maintaining and pressure-decreasing being performed using a three-position valve or two-port and two-position valve. In addition, as disclosed in the Japanese Patent Publication No. 51-6308, it is also known that the pressure-increasing and pressure-decreasing can be slowly effected under pulse-type braking hydraulic pressure control.
There is a problem which arises with such a conventional braking hydraulic pressure control system, however, in that severe pulsation of the hydraulic pressure can occur due to a shock phenomenon caused by the switching operation between the pressure-increasing, pressure-maintaining and pressure-decreasing whereby vibration is conveyed through a suspension and others to the vehicle body. This gives a discomfort sensation to the vehicle driver. Moreover, this shock phenomenon also occurs at the master cylinder side so that the vibration is transmitted to the braking pedal to similarly give a discomfort sensation to the vehicle driver.